This is the look anticipated. Below, the steps. Lots of 1/2" holes drilled and then as this is the prototype, coloured fairy lights put behind.
These lights will be good with clear or semi-opaque light-coloured marbles.
Using transparent coloured beads, white lights will be better.
Envisioned, although who knows if it is possible, a sandwich made of two forms with lights in between, leaving space for easy replacement if they burn out. These can then be hung from an arch over a roadway or in a window or in trees, anywhere there is electricity available.
The mobile idea is still in play.